EP3664068B1

EP3664068B1 - Method for acquiring charging rate of liquid crystal panel

Info

Publication number: EP3664068B1
Application number: EP17919771.0A
Authority: EP
Inventors: Sikun HAO
Original assignee: Shenzhen China Star Optoelectronics Semiconductor Display Technology Co Ltd
Current assignee: Shenzhen China Star Optoelectronics Semiconductor Display Technology Co Ltd
Priority date: 2017-08-03
Filing date: 2017-11-15
Publication date: 2023-08-23
Anticipated expiration: 2037-11-15
Also published as: JP2020527257A; KR102305271B1; PL3664068T3; JP6968277B2; KR20200034793A; CN107393453A; WO2019024323A1; CN107393453B; EP3664068A1; EP3664068A4

Description

FIELD OF THE INVENTION

The present invention relates to the field of display techniques, and in particular to a method for obtaining liquid crystal display (LCD) charging ratio.

BACKGROUND OF THE INVENTION

The liquid crystal display (LCD), or LCD panel, provides the advantages of thinness, power-saving, no radiation, and so on, and is widely applied to, such as, liquid crystal TV, smart phone, digital camera, tablet PC, PC monitor, or notebook PC, and stays as a leading technology in panel display.
The operation principle behind the LCD is to pour liquid crystal (LC) molecules between the thin film transistor (TFT) array substrate and the color filter (CF) substrate, and then apply a driving voltage to the two substrates to control the rotation direction of the LC molecules to refract the light of the backlight module r to produce the image.
Refer to Figure 1. The active area AA of the LCD has a plurality of pixels P arranged in an array, with each pixel further comprising a red sub-pixel R, a green sub-pixel G, and a blue sub-pixel B, arranged in the longitudinal direction. Each sub-pixel is electrically connected to a TFT T, the gate of the TFT T is connected to the scan line 100 extending in the lateral direction, the source is connected to the data line 200 extending in the longitudinal direction, and the drain is connected to the pixel electrode PX. Typically, a pixel P corresponds to a data line 200 and three scan lines 100, which is referred to as tri-gate architecture. Applying the gate scan signal Gate to the scan line 100 will cause all the TFTs T connected to the scan line 100 to turn on. Then, applying the data signal Data to the data line 200 will be able to write into corresponding sub-pixel to control the LC transmittance to achieve color and brightness control.
The charging ratio is an important index for LCD as the value directly affects the brightness, transmittance, display quality of the LCD. Refer to Figure 2. The charging ratio is computed as: $C_{Ratio} = (V_{pixel} / V_{data}) \times 100 %$
Wherein V_data is the voltage of the data signal Data when the gate scan signal Gate is in effect, and V_pixel is the peak value of corresponding pixel voltage after charging sub-pixel.
In general, as shown in Figure 2, the duration when the gate scan signal Gate is in effect is equal to the duration when the data signal Data is in effect. Without pre-charging, the LCD charging ration is relatively low. To increase charging ratio, as shown in Figure 3, the duration when the gate scan signal Gate is in effect can be set longer than the duration when the data signal Data is in effect. As such, in pre-charging, the LCD charging ratio is increased.
The conventional process to obtain the LCD charging ratio comprises:

identifying pixel layout;
identifying the thickness and electric parameters, such as, conductivity, dielectric constant, and so on, of each film layer forming the pixel;
extracting related electric parameters of resistors, capacitors;
establishing a model card of the TFT based on the TFT characteristics inside the sub-pixel;
establishing a SPICE model based on the LCD driving method;
obtaining pixel voltage by analogy, and computing charging ratio.

The aforementioned conventional method has obvious shortcoming: the charging ratio only has simulation result, the accuracy cannot be ensured, and cannot be verified through experiment.
CN 102213848A discloses a method and a system for measuring transmissivity of a liquid crystal display panel, which relates to a technical field of liquid crystal display and improves measuring precision of a transmissivity curve of the liquid crystal display panel.

SUMMARY OF THE INVENTION

The object of the present invention is to provide a method for obtaining LCD charging ratio, with higher accuracy, applicable to verifying accuracy of the results obtained by using the conventional method for obtaining LCD charging ratio.
To achieve the above object, the present invention provides a method for obtaining LCD charging ratio, which comprises:

Step S1: providing an LCD;
Step S2: measuring V-T curve of the LCD, a voltage corresponding to a peak of the V-T curve being a data signal voltage;
Step S3: lighting up heavy-duty image and light-duty image of the LCD according to a same grayscale respectively, measuring and recording actual display brightness of the heavy-duty image and the light-duty image;
Step S4: computing a ratio between the actual display brightness of the heavy-duty image and the actual display brightness of the light-duty image;
Step S5: using the ratio between the actual display brightness of the heavy-duty image and the actual display brightness of the light-duty image as a ratio to find and mark a measure point on the V-T curve forming the ratio with the peak, voltage corresponding to the measure point being peak value of pixel voltage;
Step S6: computing the LCD charging ratio according to the peak value of pixel voltage and data signal voltage; $C_{Ratio} = (V_{pixel} / V_{data}) \times 100 %$

Wherein C_Ratio being LCD charging ratio, V_data being the voltage of the data signal, and V_pixel being the peak value of pixel voltage.
According to a preferred embodiment of the present invention, the light-duty image is a white image.
According to a preferred embodiment of the present invention, the heavy-duty image comprises a single-color red image, a single-color green image, and a single-color blue image.
According to a preferred embodiment of the present invention, in Step S3, the lighting up the light-duty image is achieved by lighting up the single-color red image, the single-color green image, and the single-color blue image sequentially.
According to a preferred embodiment of the present invention, in Step S4, computing a ratio between the actual display brightness of the heavy-duty image and the actual display brightness of the light-duty image uses the following equation: ${Lv}_{Ratio} = ({Lv}_{R} + {Lv}_{G} + {Lv}_{B}) / {Lv}_{W}$
wherein Lv_Ratio is the atio between the actual display brightness of the heavy-duty image and the actual display brightness of the light-duty image, Lv_R is the actual display brightness of the single-color red image, Lv_G is the actual display brightness of the single-color green image, Lv_B is the actual display brightness of the single-color blue image, and Lvw is the actual display brightness of the white image.
According to a preferred embodiment of the present invention, the same grayscale used in Step S3 is grayscale 255.
According to a preferred embodiment of the present invention, the white image, the single-color red image, the single-color green image, and the single-color blue image are all stored in pre-charging process.
The present invention also provides a method for obtaining LCD charging ratio, which comprises:

Step S1: providing an LCD;
Step S2: measuring V-T curve of the LCD, a voltage corresponding to a peak of the V-T curve being a data signal voltage;
Step S3: lighting up heavy-duty image and light-duty image of the LCD according to a same grayscale respectively, measuring and recording actual display brightness of the heavy-duty image and the light-duty image;
Step S4: computing a ratio between the actual display brightness of the heavy-duty image and the actual display brightness of the light-duty image;
Step S5: using the ratio between the actual display brightness of the heavy-duty image and the actual display brightness of the light-duty image as a ratio to find and mark a measure point on the V-T curve forming the ratio with the peak, voltage corresponding to the measure point being peak value of pixel voltage;
Step S6: computing the LCD charging ratio according to the peak value of pixel voltage and data signal voltage; $C_{Ratio} = (V_{pixel} / V_{data}) \times 100 %$
- wherein C_Ratio being LCD charging ratio, V_data being the voltage of the data signal, and V_pixel being the peak value of pixel voltage;
- wherein the light-duty image being a white image;
- wherein the heavy-duty image comprising a single-color red image, a single-color green image, and a single-color blue image;
- wherein in Step S3, the lighting up the light-duty image being achieved by lighting up the single-color red image, the single-color green image, and the single-color blue image sequentially;
- wherein the white image, the single-color red image, the single-color green image, and the single-color blue image being all stored in pre-charging process.

The present invention provides the following advantages: the invention provides a method for obtaining LCD charging ratio, comprising: measuring V-T curve of the LCD, a voltage corresponding to a peak of the V-T curve being a data signal voltage; lighting up heavy-duty image and light-duty image of the LCD according to a same grayscale respectively, measuring and recording actual display brightness of the heavy-duty image and the light-duty image; computing a ratio between the actual display brightness of the heavy-duty image and the actual display brightness of the light-duty image; using the ratio between the actual display brightness of the heavy-duty image and the actual display brightness of the light-duty image as a ratio to find and mark a measure point on the V-T curve forming the ratio with the peak, voltage corresponding to the measure point being peak value of pixel voltage; computing the LCD charging ratio according to the peak value of pixel voltage and data signal voltage. As such, the accuracy is high and applicable to verifying accuracy of the results obtained by using the conventional method for obtaining LCD charging ratio.

BRIEF DESCRIPTION OF THE DRAWINGS

To make the technical solution of the embodiments according to the present invention, a brief description of the drawings that are necessary for the illustration of the embodiments will be given as follows. Apparently, the drawings described below show only example embodiments of the present invention and for those having ordinary skills in the art, other drawings may be easily obtained from these drawings without paying any creative effort. In the drawings:

Figure 1 is a schematic view showing a known tri-gate architecture LCD with active areas;
Figure 2 is a schematic view showing the timing sequence without pre-charging process for the LCD of Figure 1;
Figure 3 is a schematic view showing the timing sequence with pre-charging process for the LCD of Figure 1;
Figure 4 is a schematic view showing the flowchart of a preferred embodiment of the method for obtaining LCD charging ratio of the present invention;
Figure 5 is a schematic view showing the V-T curve used in a preferred embodiment of the method for obtaining LCD charging ratio of the present invention;
Figure 6 is a schematic view showing lighting up a white image in a preferred embodiment of the method for obtaining LCD charging ratio of the present invention;
Figure 7 is a schematic view showing the timing sequence corresponding to Figure 6;
Figure 8 is a schematic view showing lighting up a single-color green image in a preferred embodiment of the method for obtaining LCD charging ratio of the present invention;
Figure 9 is a schematic view showing the timing sequence corresponding to Figure 8;
Figure 10 is a schematic view showing the principle of method for obtaining LCD charging ratio of the present invention.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

Referring to Figure 4, Figure 4 is a schematic view showing the flowchart of a preferred embodiment of the method for obtaining LCD charging ratio of the present invention. The method comprises:
Step S1: providing an LCD.
The LCD is a tri-gate architecture LCD as shown in Figure 1, wherein the active area is disposed with a plurality of pixels P arranged in an array, with each pixel further comprising a red sub-pixel R, a green sub-pixel G, and a blue sub-pixel B, arranged in the longitudinal direction. Each sub-pixel is electrically connected to a TFT T, the gate of the TFT T is connected to the scan line 100 extending in the lateral direction, the source is connected to the data line 200 extending in the longitudinal direction, and the drain is connected to the pixel electrode PX. Typically, a pixel P corresponds to a data line 200 and three scan lines 100. Applying the gate scan signal Gate to the scan line 100 will cause all the TFTs T connected to the scan line 100 to turn on. Then, applying the data signal Data to the data line 200 will be able to write into corresponding sub-pixel to control the LC transmittance to achieve color and brightness control.
Step S2: as shown in Figure 5, measuring V-T curve of the LCD (V is the voltage and T is the transmittance ratio).
The voltage corresponding to a peak D1 of the V-T curve is a data signal voltage V_data.
Step S3: as shown in Figure 6 and Figure 8, lighting up heavy-duty image and light-duty image of the LCD according to a same grayscale respectively, measuring and recording actual display brightness of the heavy-duty image and the light-duty image.
Specifically, the same grayscale used is preferably grayscale 255.
The light-duty image is a white image; that is, the red sub-pixel R, the green sub-pixel G and the blue sub-pixel B are all lighted up at grayscale 255. Refer to Figure 6 and Figure 7. The light-duty image for lighting up the LCD is stored in the pre-charging process, and the pre-charging voltage is higher. The final peak value V_pixel of pixel voltage can reach the data signal V_data.
The heavy-duty image comprises a single-color red image, a single-color green image, and a single-color blue image. In Step S3, the lighting up the light-duty image is achieved by lighting up the single-color red image, i.e., lighting up red sub-pixel R at grayscale 255, the single-color green image i.e., lighting up green sub-pixel G at grayscale 255, and the single-color blue image, i.e., lighting up blue sub-pixel B at grayscale 255, sequentially. Refer to Figure 8 and Figure 9. The heavy-duty image (take the single-color green image as example) for lighting up the LCD is stored in the pre-charging process, and the pre-charging voltage is lower. The final peak value V_pixel of pixel voltage is lower than the data signal V_data.
Step S4: computing a ratio between the actual display brightness of the heavy-duty image and the actual display brightness of the light-duty image.
Specifically, in Step S4, computing a ratio between the actual display brightness of the heavy-duty image and the actual display brightness of the light-duty image uses the following equation: ${Lv}_{Ratio} = ({Lv}_{R} + {Lv}_{G} + {Lv}_{B}) / {Lv}_{W}$
wherein Lv_Ratio is the ratio between the actual display brightness of the heavy-duty image and the actual display brightness of the light-duty image, Lv_R is the actual display brightness of the single-color red image, Lv_G is the actual display brightness of the single-color green image, Lv_B is the actual display brightness of the single-color blue image, and Lvw is the actual display brightness of the white image.
Step S5: as shown in Figure 5, using the ratio between the actual display brightness of the heavy-duty image and the actual display brightness of the light-duty image as a ratio to find and mark a measure point D2 on the V-T curve forming the ratio with the peak D1, voltage corresponding to the measure point D2 being peak value of pixel voltage V_pixel.
Step S6: computing the LCD charging ratio according to the peak value of pixel voltage and data signal voltage; $C_{Ratio} = (V_{pixel} / V_{data}) \times 100 %$
Wherein C_Ratio being LCD charging ratio, V_data being the voltage of the data signal, and V_pixel being the peak value of pixel voltage.
Refer to Figure 10, in combination with Figure 5. The principle of the method for obtaining the LCD charging ratio is as follows:
Because the heavy-duty image (e.g., the single-color green image) is insufficiently charged, the actual display brightness at 255 grayscale is less than the actual display brightness of the white image at 255 grayscale. For example, the actual display brightness of the single-color green image at 255 grayscale is only 91% of the actual display brightness of the white image at 255 grayscale; that is, the actual display brightness of the single-color green image at 255 grayscale is equal to the actual display brightness of the white image at 232 grayscale. The brightness equality correspondingly means equal peak value V_pixel of pixel voltage, and the brightness corresponds to transmittance ratio. As such, using the ratio between the actual display brightness of the heavy-duty image and the actual display brightness of the light-duty image as a ratio to find and mark a measure point D2 on the V-T curve forming the ratio with the peak D1, voltage corresponding to the measure point D2 is peak value of pixel voltage V_pixel. Then, by computing the ratio between the peak value V_pixel of pixel voltage and data signal voltage V_data, the LCD charging ratio C_Ratio is obtained. This method obtains LCD charging ratio through actual measurement so that the accuracy is higher and applicable to verifying accuracy of the results obtained by using the conventional method for obtaining LCD charging ratio.
In summary, the invention provides a method for obtaining LCD charging ratio, comprising: measuring V-T curve of the LCD, a voltage corresponding to a peak of the V-T curve being a data signal voltage; lighting up heavy-duty image and light-duty image of the LCD according to a same grayscale respectively, measuring and recording actual display brightness of the heavy-duty image and the light-duty image; computing a ratio between the actual display brightness of the heavy-duty image and the actual display brightness of the light-duty image; using the ratio between the actual display brightness of the heavy-duty image and the actual display brightness of the light-duty image as a ratio to find and mark a measure point on the V-T curve forming the ratio with the peak, voltage corresponding to the measure point being peak value of pixel voltage; computing the LCD charging ratio according to the peak value of pixel voltage and data signal voltage. As such, the accuracy is high and applicable to verifying accuracy of the results obtained by using the conventional method for obtaining LCD charging ratio.

Claims

A method for obtaining liquid crystal display (LCD) charging ratio, comprising:
Step S1: providing an LCD; and

Step S2: measuring V-T curve of the LCD, a voltage corresponding to a peak (D1) of the V-T curve being a data signal voltage (V_data);
wherein the method is characterized in that the method further comprises:

Step S3: lighting up heavy-duty image and light-duty image of the LCD according to a same grayscale respectively, measuring and recording actual display brightness of the heavy-duty image and the light-duty image;

Step S4: computing a ratio between the actual display brightness of the heavy-duty image and the actual display brightness of the light-duty image;

Step S5: using the ratio between the actual display brightness of the heavy-duty image and the actual display brightness of the light-duty image as a ratio to find and mark a measure point on the V-T curve forming the ratio with the peak, voltage corresponding to the measure point being peak value (V_pixel) of pixel voltage; and

Step S6: computing the LCD charging ratio according to the peak value (V_pixel) of pixel voltage and data signal voltage (V_data); $C_{Ratio} = (V_{pixel} / V_{data}) \times 100 %;$

wherein C_Ratio being LCD charging ratio, V_data being the voltage of the data signal, and V_pixel being the peak value of pixel voltage;

wherein the heavy-duty image comprises a single-color red image, a single-color green image, and a single-color blue image, and wherein the light-duty image is a white image.
The method for obtaining LCD charging ratio as claimed in claim 1 characterized in that in Step S3, the lighting up the light-duty image is achieved by lighting up the single-color red image, the single-color green image, and the single-color blue image sequentially.
The method for obtaining LCD charging ratio as claimed in any of Claims 1-2 characterized in that in Step S4, computing a ratio between the actual display brightness of the heavy-duty image and the actual display brightness of the light-duty image uses the following equation: ${Lv}_{Ratio} = ({Lv}_{R} + {Lv}_{G} + {Lv}_{B}) / {Lv}_{W};$
wherein Lv_Ratio is the ratio between the actual display brightness of the heavy-duty image and the actual display brightness of the light-duty image, Lv_R is the actual display brightness of the single-color red image, Lv_G is the actual display brightness of the single-color green image, Lv_B is the actual display brightness of the single-color blue image, and Lvw is the actual display brightness of the white image.
The method for obtaining LCD charging ratio as claimed in any of Claims 1-2 characterized in that the same grayscale used in Step S3 is grayscale 255.
The method for obtaining LCD charging ratio as claimed in claim 1 characterized in that the white image, the single-color red image, the single-color green image, and the single-color blue image are all stored in pre-charging process.